Water Hardness in 94403
San Mateo, California · San Mateo County
Based on laboratory testing of treated tap water reported to state regulators. Updated periodically with the latest compliance data.
Our Estimate
Weighted average from 19 water systems.
What This Means For You
Hard Water - Treatment Recommended
Your water is hard. Scale buildup is likely affecting your plumbing and appliances, reducing their lifespan and efficiency. A water softener is recommended to protect your home.
Recommended Products
Learn more: Do I Need a Water Softener? | Salt-Based vs Salt-Free | Size Calculator | How to Test Your Water
Know your water hardness?
If you've tested your water or have your utility's CCR report, share your reading to help us improve accuracy for San Mateo, CA (94403).
Water Systems Serving 94403
Nearby Zip Codes
Frequently Asked Questions
Is the water hard in San Mateo, CA (94403)?
The average water hardness in 94403 is 241 PPM (14.1 GPG), which is classified as hard.
Do I need a water softener in 94403?
With hardness of 241 PPM, a water softener is recommended for homes in 94403.
How many water systems serve 94403?
Zip code 94403 in San Mateo, California is served by 19 water systems.
Learn More About Your Water
Best Water Softeners 2026: Top Picks for Every Budget
We compared salt-based, salt-free, and portable water softeners. Here are our top picks based on water hardness level, home size, and budget.
12 min readWater Softener Size Calculator: What Grain Capacity Do You Need?
Calculate the right water softener size for your home. Enter your household size and water hardness to get a grain capacity recommendation.
7 min readHard Water and Hair: Effects, Damage Signs & What Actually Helps
How mineral buildup affects your hair - and what to do about it based on your actual water hardness level.
10 min read